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ZyXEL uses a transformer that is a 120V AC, 60Hz, 23.4W model that outputs 
20VAC, 900mA with a center tap.

The transformer should ideally have output between 50 Hz and 60 Hz.

                +-----+
        AC -->  | o o | <-- AC
                 \ o /
                  ---
                   ^
                   +-- Center tap

Michael Chua Boon Wei (chuabw@singnet.com.sg) has a power supply that is a
240V AC, 50 Hz, 27.5W model that outputs 21V AC, 900 mA.  It has the same
pinout as above.

Michael Kuhl (mkuhl@newbridge.com) and Robert Wong (rwong@direct.ca) has a 
slightly different power supply that is a 120V AC, 60 Hz, 12.5W model that 
outputs 9V AC, 1000mA.  It is also described as a Class 2 Transformer, 
Part No. 30-111-011496, Model No. A48091000 transformer.  Also, the pinout is
slightly different.

             +-----+
     AC -->  | o o |  <-- No connection
              \ o /
               ---
                ^
                +-- AC


Alan Brown (alan@papaioea.manawatu.gen.nz) has a power supply (non-ZyXEL)
that is a 230V AC, 50 Hz model that outputs 14V AC.  The shape of the
connector is a cylindrical 2.5mm coaxial power socket seen on many other 
pieces of electronic equipment.

ZyXEL modems seem to accept many different voltages ranging from 9 to 20V AC.
The output voltage for the transformers may be as low as 5V AC.  Also, the 
power supply may or may not be center tapped.  Also, in countries with 
220V AC, the local suppliers supply a locally manufactured power supply.

To avoid any potential problems, use only the power supply that came with the
modem.  ZyXEL does sell power supplies for owners should they move to another
country or lose the factory power supply.

Please e-mail Robert Wong (rwong@direct.ca) if you have a different power 
supply.